Linear drive for rotary potentiometers



Feb. 21, 1961 o. BERLINER LINEAR DRIVE FOR ROTARY POTENTIOMETERS Filed Dec. 9, 1959 INVENTOR.

' OLIVER BERLINER BYW AGENT United States Patent LINEAR DRIVE FOR ROTARY POTENTIOMETERS Oliver Berliner, 1007 Roxbury Drive, Beverly Hills, Calif.

Filed Dec. 9, 1959, Ser. No. 858,481

6 Claims. (Cl. 338-67) This invention relates to potentiometers and more particularly to those used as volume controls and to novel linear driving mechanisms for such controls.

The control of the sound level, amplitude, or volume of sound signals in electrical audio circuits such as used in broadcast control boards and sound recording systems is generally accomplished by means of a rotatable potentiometer.

From a human engineering standpoint, it is a more difficult and complex manual operation to rotate a knob on such a rotatable potentiometer for the adjustment of level than it would be to push a handle in a relatively straight line path to accomplish the level adjustment.

This invention contemplates the adjustment of volume level or loudness in such equipment as broadcast audio control panels by providing levers or handles which can be pushed in a generally straight line direction to adjust a rotatable control potentiometer as desired.

In the prior art linear potentiometers have been provided wherein the resistance element of the potentiometer or control is wound on, or sprayed on a straight-line core and in which complex wiper mechanisms are provided to contact the straight line resistance element directly. While such linear wound potentiometers are excellent devices for the purpose they are extremely expensive because they are diificult to manufacture.

The manufacture of potentiometers with rotatable wiper elements controlled from a rotary shaft on which the wiper is mounted has advanced to such a mass production stage that such controls are both inexpensive and widely available.

This invention further contemplates provision of low cost mechanisms which may be attached to the inexpensive rotary potentiometers to make them adjustable by a generally linear motion of a lever or a bar or by an arcuate motion over such a small sector as to be nearly linear.

With linear potentiometers equipped according to this invention, the advantages would be great since a mass produced and inexpensive article could be produced for use in the same manner as one which is more costly.

It is an object of this invention to provide linear drive devices for rotary potentiometers in which the rotary shaft of such. potentiometers can be rotated by a relatively straight-line movement of the linear drive device.

It is another object of this invention to provide a drive device which by movement of a lever over an are limited to no more than 90, the full rotation of a rotatable potentiometer can be accomplished.

It is a further object of this invention to provide a linear drive for a rotary potentiometer utilizing a gear arrangement of suitable ratio.

It is still another object of this invention to provide a rack and pinion type of drive to generate the rotary motion of the shaft of a rotatable potentiometer.

It is still further object of this invention to provide a plurality of linear drive potentiometers equipped accord- 2,972,725 Patented Feb. 21, 1961 ing to this invention and mounted in an audio control panel in an array of conveniently operable units.

These and other objects of this invention will become clearly evident from the specification which follows taken together with the accompanying drawing, in which:

Figure 1 is a view of an assembly of one of the rotary potentiometer lever arm control and gear elements in an embodiment according to this invention as it appears when viewed from the side behind a vertical panel in which it is installed;

Figure 2 is a perspective view of the assembly of Figure 1 shown removed from the panel;

Figure 3 is a view of a panel showing alternative methods of utilizing a plurality of embodiments of the invention in a studio audio control unit;

Figure 4 is a side view of another embodiment of the invention attached to a panel in the horizontal position; and

Figure 5 is a cross-sectional view through 5-5 of Figure 4.

Referring now to Figure l and Figure 2, taken together, wherein one embodiment of a linear audio potentiometer control mechanism according to this invention is shown, L-shaped brackets 10 and 10A may be seen mounted on a base 11, normally having a right angle bend as shown at 15. Brackets 10, 10A are assembled immovably to base 11 by screws 12. Base 11 by its right angle bend 15 is assembled to a panel 13 shown in further detail in Figure 3. The panel 13 is slotted as at 16 to receive a lever arm 23 as further described below. The assembly of 15 to 13 can be by welding or riveting or any other known method. Fixedly mounted to bracket 10 is a potentiometer 17 which has a rotatable shaft 18 and contact terminals 19 to which may be wired typical electrical circuits in which audio signals may be controlled by potentiometer 17 in accordance with wellknown practices in the art of sound recording and radio broadcasting. Attached to shaft 18 is a pinion gear 20. In bracket 10A a gear support, shaft 22 is mounted so that it is immobile. Shaft 22 is of such a length as to extend over the length of a panel such as 13, shown in Figure 3. When so used, a plurality of gears such as 21 are rotatably mounted on the shaft at predetermined spaced intervals. Gears such as 21 mesh with gears such as 20 mounted on associated potentiometer assemblies such as 17, 18, 19, and 10 and each assembly is positioned with respect to each gear 21 so that each gear 20, respectively, is driven by a respective gear 21. The operation of each gear 21 is independent and selective. To each gear such as 21 is attached the lever 23. Movement of lever 23 over an arc of as shown in Figure 1, will rotate the gear 20 over an arc of 270 by it's meshing with gear 21. The maximum rotation of standard potentiometer shafts such as 20 on standard potentiometers such as 17 is 270. Lever arm 23 is tipped with a knob 24 which, as may be seen in the Figures 1 and 3, protrudes from panel 13 through slot 16. Each of the linear potentiometer assemblies according to this invention mounted in panels such as 13 is equipped with a knob such as 24.

Referring now to Figure 3, panel 13 may be seen to contain control knobs, such as 31, which may be used for master gain control or any other function and one or more meters, such as 32, to indicate the levels of audio signals passing through an audio system of which panel 13 may be a part. A number of slots, 16, are cut in panel 13. Attenuation scale factor markings 33 are inscribed along side of slots 16. To the right of the panel 13 a portion of a panel 13A is shown to illustrate the ditference in appearance of the panel when using the embodiment of Figures 4 and 5 as described further below. Markings 33A and slot 16A correspond to simil ar markings 33 and 16 on panel 13. The knob of control 31A corresponds to the knob of control 31 on panel 13.

As indicated on panel 13, the view of Figure 1 is taken through 1-1, on the panel. Figure 4 is taken through 44 on the panel. I

Panels 13 and 13A represent typical installation techniques but others may occur to those skilled in the art who choose to use linear otentiometers according to this invention.

Referring now to Figures 4 and 5 wherein Figure 5 shows a cross-section through 5-5 of Figure 4, the potentiometer 17 with its lead terminals 19, shaft 18 and pinion gear 20 is the same as that shown in Figures '1 and 2. While not indicated in Figures 4 and 5, a bracket similar to or 10A would be required on which to mount the potentiometer 17 in some appropriate relation to the panel and its driving gear rack 25 further described below. The mounting may consist of a bracket with a generally rectangular series of bends to form a J on which the potentiometer is supported.

The gear-toothed driving rack 25 is provided to engage gear for rotation of shaft 18 of potentiometer 17 to ad just the potentiometer. As may be seen in Figure 5, rack is shaped to ride on gear support guides 29 and in a position to be in engagement with gear 20. Ball or roller bearings 27 and 28 may be used to provide smoother movement of drive gear rack 25 as it rides back and forth in the direction of arrow 35. Attached to rack 25 is a lever arm 23A with knob 24A at one end. Motion of arm 23A in direction of arrow in slot 16A of panel 13A moves rack 25 which rotates gear 20 and in turn rotates shaft 18 of potentiometer 17 to adjust potentiometer 17.

The operation of the linear potentiometer control mechanisms described above may be seen to be as follows:

The potentiometer 17 is normally connected by its terminals 19 to an audio circuit of a control system as has been set forth above. When that audio circuit requires adjustment so that the sound level is not in excess of a predetermined limit, or in order to increase the level when below a predetermined limit, the knob 24 is pushed which in turn moves lever arm 23. If the control shown in Figures 1 and 2 is used, arm 23 which is fixedly attached to drive gear 21 will rotate drive gear 21 when moved to the dashed position shown in Figure 1. Gear 21 is free to move on fixed gear support shaft 22 to mesh with gear 20. Gear 20, being tightly attached to shaft 18 will rotate shaft 18 and adjust the position of the wiper of potentiometer 17 with respect to its terminal ends to select an appropriate proportion of the signal energy from a source, not shown, to a utilization circuit, not shown. The source would be from a microphone, playback, or transmission line for sound signals. The utilization circuit would be an amplifier. Both of these are well-known to the pertinent arts.

If the linear potentiometer control mechanism of this invention shown in Figures 4 and 5 should be used, the operation will be essentially as shown in Figure 4. Motion of lever arm 23A by application of pressure against knob 24A will result in movement of arm 23A in slot 16A of panel 13A. Lever arm 23A is attached to drive gear rack 25 which rides in gear support guide rails 29 and 30 with reduced friction due to the presence of ball bearings 27 and 28 to rotate gear 20 with which rack 25 meshes to turn shaft 18 of potentiometer 17 for level adjustment of audio signals in circuits which may be connected to terminals 19.

A plurality of microphones or tape signal sources of audio lines, or phonograph record player signal sources,

etc. may be used in most audio control consoles. The arrangements shown in Figure 3 and identified as panels 13 and 13A, respectively illustrate representative assemblies of a plurality of controls using the linear potentiometer drive control mechanisms according to this invention. The specific layouts or configurations of the control mechanisms may vary as suits the circuit needs or aesthetic design tastes of the user.

What is claimed as new is:

1. A relatively linearly movable drive mechanism for a potentiometer having a rotatable control shaft comprising in combination: a potentiometer having a first and a second terminal and a slidable terminal movable between said first and said second terminals across a resistance element connected between said first and second terminals to provide selective adjustment of the resistance between a selected one of said first and second terminals and said slidable terminal moving therebetween; a rotatable shaft coupled with said slidable terminal to move said slidable terminal across said resistance element when said shaft is rotated; a pinion gear attached to said rotatable shaft; a driving gear assembled in meshing relation with said pinion gear to a fixed gear support; and a lever arm fixedly attached to said driving gear, said fixed gear support and said potentiometer being assembled in operatable relation on a base member attached to a control panel, whereby said lever arm acting against said driving gear rotates said pinion and thereby rotates said slidable terminal of said potentiometer to adjust the resistance between said slidable terminal and said selected one of said first and second terminals.

2. The drive mechanism defined in claim 1 wherein said driving gear is a spur gear having a 4 to 1 tooth ratio to said pinion gear, and said spur gear is supported on a fixed shaft, said spur gear being rotatably mounted on said fixed shaft to drive said pinion gear.

3. The drive mechanism defined in claim 1 wherein said driving gear is a linear rack supported on a rack guide, said linear rack being movably assembled in said rack guide to drive said pinion gear.

4. In an audio control panel a relatively linearly movable drive mechanism for a potentiometer having a rotatable control shaft, said drive mechanism comprising the combination of a potentiometer having a rotatable shaft to adjust the resistance thereof between selected points thereof; a pinion gear attached to said rotatable shaft; a base member having supporting brackets mounted thereon, said potentiometer being assembled in one of said brackets; a driving gear movably assembled in another of said brackets in a meshing relation with said pinion gear; and a lever arm fixedly attached to said driving gear; said driving gear, said pinion gear, and said potentiometer being assembled in operable relation on said base member said member being attached to the control panel.

5. The drive mechanism defined in claim 4 wherein said driving gear is a spur gear having at least a 4 to l tooth ratio to said pinion gear, and said spur gear is supported on a fixed shaft, said spur gear being rotatably mounted on said fixed shaft to drive said pinion gear.

6. The drive mechanism defined in claim 4 wherein said driving gear is a linear rack supported on a rack guide, said linear rack being movably assembled in said rack guide to drive said pinion gear.

References Cited in the file of this patent UNITED STATES PATENTS 981,452 McNally Jan. 10, 1911 2,273,760 Nelson Feb. 17, 1942 2,808,734 Ortner Oct. 8, 1957 2,820,872 Carr Ian. 21, 1958 

